Transcript Lehr CFP wireless Talk Oct2009 - MIT

Wireless, spectrum scarcity, and
expanding our notions of sharing….
William Lehr
Communications Futures Program
Massachusetts Institute of Technology
[email protected]
*John Chapin
(RLE)
[email protected]
CFP All-Members’ Meeting: ‘Pent-up Disruptions: Communications in a new era’
October 28-29th, 2009
MIT Stata Center
Cambridge MA
© Lehr & Chapin, 2009
How will wireless evolve? Like wired, maybe?
Wired broadband is evolving to a common platform architecture
General purpose, fiber-rich, Everything-over-IP
Wireless broadband is evolving differently
No single platform, due to persistent technical differences
Table 1 Persistent Key Differences in Wired vs. Wireless Networking
Wired
Wireless
Capacity
Abundant
Scarce
Topology
Point-to-point
Broadcast
Reliability
Reliable
Unreliable
Mobility
Fixed
Mobile
If wireless is not evolving like wired, then how will it evolve?
Key driver: spectrum scarcity…..
© Lehr & Chapin, 2009
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Hybrid Wireless Broadband
Application
Voice
TV
L3 Net
Switched Voice
1way Broadcast
IP
L1/2 Link
New Air Interface
MediaFLO, DVB
LTE, WiMax, etc
Media
Voice
Video
Data
Operator’s licensed spectrum + shared spectrum (DSA, unlicensed)
A single broadband service provider uses:
Hybrid wireless network types
Mix of application-specific networks and generic data networks
Hybrid spectrum rights
Mix of exclusive, shared, unlicensed, short-term leases, secondary, ...
Continuous spectrum reallocation
Among the operator’s own networks and applications
Across independent operators/regimes via markets, private commons, ...
© Lehr & Chapin, 2009
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Why is the future of wireless broadband “hybrid”?
Current 3G service providers are already hybrid
Smartphones provide converged access to (e.g.)
Voice-specialized network
GSM
Generic data network
3G HSPA
Unlicensed spectrum
WiFi, Bluetooth, GPS
Network shared among operators
MediaFLO
(Spectrum sharing and reallocation is embyronic)
Prediction: this will continue
(LTE vision notwithstanding)
Specialized networks are more spectrally efficient
Prediction: operators will not be able to acquire/afford enough
exclusively licensed spectrum to meet demand
c.f. ITU-R wp8F M.2078, recent auction valuations
Spectrum sharing (of all types) will become critical for core services
© Lehr & Chapin, 2009
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Future is shared spectrum
decoupling of spectrum frequencies
from applications (& infrastructure)
Domain
Trend is towards
aka
“Dynamic
Spectrum Access”
(DSA)
Drivers and Enablers
Technology
(capabilities)
Frequency agility
Improved capability for
spectrum sharing
Smart radio systems
OFDM and spread spectrum
Growth of fast data networks
Revenue
(customer experience)
24/7 availability
Simplicity of use
Seamless mobility
Heterogeneous networks
3G+WiFi, wireless+wired
global roaming
Costs
Lower costs per byte
Intermodal competition
Bursty traffic, Multimedia
services, Fat-tailed usage
profiles, Mergers & Acquisitions
Reduction of artificial
scarcity
Technology neutrality
Market-based licensing
Unlicensed spectrum mgmt
(provisioning)
Policy
(spectrum reform)
© Lehr & Chapin, 2009
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Why hybrid sharing model makes sense…
Shared spectrum
-- lower cost access (too expensive to use “all dedicated,”
especially for bursty traffic)
-- some apps are delay tolerant (i.e., wait until spectrum available)
Dedicated spectrum
-- predictable interference environment  can guarantee QoS
-- some apps are not delay tolerant (need predictable access)
-- guaranteed QoS  premium service
Mix shared/dedicated  best of both worlds
-- guaranteed access for when it really has to get there…
-- match spectrum characteristics better to usage requirements
-- peak load provisioning problem (like power generation)
-- hedge your bets, low risk way to learn about sharing…
-- (more policy reform may be nice, but don’t hold your breath….)
© Lehr & Chapin, 2009
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Business models for spectrum sharing
Spectrum must be shared much more intensively!
Primary
Sharing
Non-Cooperative
Cooperative
Permission primary user not needed.
No explicit coordination.
Permission primary user needed.
Explicit coordination.
Other users look like noise.
Other signals recognizable.
Unlicensed, e.g., WiFi, Bluetooth
Secondary markets, e.g., leasing
Bandwidth Manager (real-time)
Closed commons
Secondary
Sharing
Easements:
-- underlay, e.g. UWB
-- overlay, e.g., TV White space (LBT)
© Lehr & Chapin, 2009
Bilateral contracting
*For more info, see Chapin & Lehr (2007a), Lehr (2009)
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Where to start – a sample app for mixed spectrum model????
Bulk delivery to support high-capacity smartphones
Different types of communication: time sensitive vs insensitive
“Immediate” delivery service vs “bulk” delivery service
Bulk delivery may use exclusive, shared, or unlicensed spectrum
Based on cost, delivery time, congestion, etc.
Use bulk delivery for read-ahead and write-behind. Examples:
--Trickle down email attachments before user clicks on them
-- Pre-fetch web pages that user often checks
-- Distribute content such as video in the background
-- Media library synchronization
-- Periodic backups
-- etc….
© Lehr & Chapin, 2009
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Other applications for hybrid wireless broadband
Sensor networks
Daily routine reports: shared spectrum
Urgent updates: licensed spectrum
(“earthquake detected!”)
Communications in public venues
e.g. stadiums
High-rent events: all in (temporarily) licensed spectrum
Low-rent events: small amount in licensed spectrum, most in shared
Ad-hoc networks
Control channel: licensed spectrum
• “who’s there?”
• “where is the data channel today?”
Data links: small amount in licensed, surge capacity in shared
© Lehr & Chapin, 2009
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How to make hybrid systems affordable (1)
Exploit SDR infrastructure
Single network, single base station unit
Transmits multiple carriers
Some carriers always on in exclusively licensed spectrum
Some carriers intermittent in shared spectrum (based on etiquette)
• Different air interface standards are likely required
Expected initial business structure
One operator in a market deploys shared spectrum capability
Others lease access at wholesale rates
Policy recommendation
Promote spectrum sharing in bands close to licensed bands
Frequency agility for high-power base stations is expensive
© Lehr & Chapin, 2009
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How to make hybrid systems affordable (2)
Handset / CPE challenges
Need to match economics of existing radios that have global scale
Solution: add shared-spectrum capability to existing radio designs
Use adjacent, unpaired spectrum for sharing
• Avoid adding another antenna or amplifier
Re-use existing baseband chips
Re-use existing waveforms with small modifications
• Efficiency may be low at first
• Grow to more appropriate air interfaces for sharing as momentum builds
Policy recommendation
Target ~25MHz unpaired spectrum for sharing
Near existing mobile dedicated bands below 2.5GHz
© Lehr & Chapin, 2009
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How to make hybrid systems affordable (3)
Prioritize simplicity when choosing initial bands and access rules
Establish test-beds for real-world evaluations
DSA devices are hard to verify
Consider Time-Limited Leases (Chapin & Lehr, 2007)
Certification risk increases device cost, makes developers conservative
Support research on technical mechanisms to determine the
source of intermittent interference
Assigning liability is hard when devices use dynamic spectrum sharing
Idea: “black box” that logs recent spectrum access decisions
© Lehr & Chapin, 2009
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Business models for spectrum sharing
Many models are possible
unlicensed, short-term leases, cooperative secondary access,
noncooperative secondary access, co-primary access, ...
Particularly of interest for hybrid wireless: closed commons
Multiple co-primary users
Restricted and managed access (all users agree to sharing protocol)
Predictable interference/availability
How to jumpstart experimentation with closed commons
Permit coalition bidding in auctions
• Challenging to avoid cartelization or static partitioning of license
Demonstrate success in public safety pooling
• (Lehr & Jesuale, 2008)
© Lehr & Chapin, 2009
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Summary
The future of wireless broadband is hybrid
Multiple technologies, multiple spectrum rights models
In particular, spectrum sharing will help provide core services
• Spectrum-sharing-only networks face significant economic challenges
Example applications
Bulk delivery of delay-tolerant price-sensitive data
Sensor networks, ad-hoc networks, public venues, ...
Challenges and solutions to initiate mass-market adoption
Affordability: use SDR infrastructure, spectrum near mobile bands
Certification and liability: policies to promote simplicity
Business models: investigate closed commons
William Lehr
[email protected]
© Lehr & Chapin, 2009
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References
Lehr, W. and J. Chapin (2009a) ”Hybrid Wireless Broadband," 37th Research Conference
on Communications, Information, and Internet Policy (TPRC), Arlington, VA,
September 26, 2009.
Lehr, W. and J. Chapin (2009b) "Rethinking wireless broadband platforms," invited
paper presented at "Wireless Technologies: Enabling Innovation and Growth,"
Georgetown Center for Business and Public Policy, Washington DC, April 17, 2009.
Lehr, W. and N. Jesuale (2008) "Public Safety Radios Need to Pool Spectrum," IEEE
Communications Magazine, March 2009.
Chapin, J. and W. Lehr (2007a), "The path to market success for dynamic spectrum
access technology," IEEE Communications Magazine, Special Feature on Cognitive
Radios for Dynamic Spectrum Access, May 2007.
Chapin, J. and W. Lehr (2007b), "Time Limited Leases for Innovative Radios,"
proceedings of IEEE DySPAN2007, Dublin, April 18-20, 2007 and IEEE
Communications Magazine, June 2007.
© Lehr & Chapin, 2009
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Some additional back-up slides…
© Lehr & Chapin, 2009
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Predicted spectrum needs by 2020
Spectrum requirements (MHz) for cellular voice and data
Allocations must be below 5 GHz
2020
Europe, Middle
East, and Africa
Americas
Asia-Pacific, Iran
Demand
model
Predicted
Total
2006
Increase
2006
Increase
2006
Increase
Low
1280
693
587
723
557
749
531
High
1720
693
1027
723
997
749
971
Source: ITU-R Working Party 8F
Report M.2078 [IMT.ESTIMATE]
May, 2006
© Lehr & Chapin, 2009
Analysis included
• Traffic projections and requirements
• Service and application requirements
• Spectrum efficiency
• Radio transmission characteristics
• Harmonized use of spectrum
• Technical solutions to facilitate global roaming
• Sharing and compatibility analysis
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